Groundwater as an Alternative?

MacDonald et al (2009) describes surface water as becoming increasingly unreliable, and it is because of this that we need to look elsewhere for more resilient and sustainable water supplies. Groundwater is responding to this need as a ‘reliable and flexible irrigation supply’ (Villholth 2013: 369) and is perhaps the most promising alternative to surface water. Taylor et al (2009) goes into a substantial amount of detail surrounding groundwater, clearly outlining the pros and cons of this resource. One of the main advantages of using groundwater is down to it being the largest store of freshwater on the planet, therefore it makes sense to use this store as opposed to the increasingly variable surface water supplies. This is especially true in arid and semi-arid regions of Africa where increased evapotranspiration and decreased or delayed precipitation as a result of climate change has already left some communities completely absent of surface water all together. Groundwater on the other hand is proven to be a more reliable source than surface water, due to it’s ability to be maintained and stored in aquifers during periods of little or no rainfall (MacDonald et al 2011). However, the sustainability of groundwater remains unclear (Taylor et al 2009), as explained in Edmund’s (2009: 781) paper where it is stated that ‘the non-renewability of many groundwater sources [are] now being exploited across the arid and semi-arid regions of Africa’, therefore the ability of groundwater to alleviate water scarcity also remains unclear.

The results from a study on groundwater recharge in Tanzania allow me to end this blog on a more optimistic note. Taylor et al (2013) found a non-linear relationship between recharge and rainfall, where it was shown that intense precipitation contributed to recharge at a disproportionate rate. As explained in an earlier blog post, many parts of Africa are expected to experience more intense precipitation as a result of climate change. Therefore, the associated increase in recharge should subsequently sustain groundwater levels for future use, providing Africa with a feasible adaptation to the increased variability in surface water.

So, What are the Implications of this Decrease in Surface Runoff?

Any projected decrease in surface runoff and water resources in general as a result of climate change will have huge implications for future agricultural, industrial and domestic water use. The domestic implications can clearly be seen in the previous case study of Polokwane, South Africa. The urgent need to reduce future water demand in the town means that the authorities are having to discourage any improvement of the water infrastructure (Cullis et al 2011). Even though the technology is there, there is currently no provision indoor taps throughout the town, meaning that most residents get their water from community taps which has the intentional effect of preventing increases in water demand. Naturally, this has significant knock on effects for domestic and industrial water use respectively, not only for the populations in terms of their standard of living, but it also effects the towns industry and economic growth.

Agriculture accounts for approximately 83.1% of total water water withdrawals, therefore it is extremely important to understand how changes in precipitation and evapotranspiration will effect food security in Africa. Rainfed crops such as maize make up a large proportion Africa’s agriculture (Giordano 2006), making Africa’s food security extremely vulnerable to climate change (Desanker 2002). This is also made worse by the fact that one third of Africa’s total income is derived from agriculture (Desanker 2002), therefore significant changes to crop yield will have considerable effects for Africa’s economy and future growth. The IPCC Fifth Assessment (2014) reaffirms this statement and goes on to say that Sub-Saharan Africa is expected to experience maize yield losses of around 22%, with some countries such as Zimbabwe experiencing losses of up to 30%.

The strain that changes in evapotranspiration and precipitation will have on the consistency and reliability of crops is an important issue in itself, however when projected population change is taken into account, the situation looks a lot more alarming. According to Gerland et al (2014), by 2050 Sub-Saharan Africa’s population is expected to have dramatically increased to 2.5 billion people, more than double of what it is today. The strain that this exponential population increase coupled with more variable water resources will place huge pressure on water resources. It is therefore crucial to deliver a sustainable solution that will help ensure Africa’s future crop yield and food security, along with industrial and domestic water needs

Changes in Surface Water continued...

In a similar study on South Africa by Cullis et al (2011), they discussed the problems that a reduction in river runoff as a result of climate change will have on the town on Polokwane in northeast South Africa. Out of the 41 Sub-Saharan African nations, South Africa ranks at having the 5^th lowest water availability, with some parts of the nation already experiencing water scarce conditions (DWAF 2004). South Africa’s highly variable and low levels of precipitation present a huge ‘limitation to the potential for growth and development of the country’ (Cullis et al 2011: 438). Models used to project river runoff in the Olifants River found that in the driest areas of the catchment, annual runoff would decrease by 33% in 2025 and by 47% in 2050. The driest areas in Letaba catchment are expected to experience a 19% decrease in 2025 and a 31% decrease by 2050. These dramatic decrease would cause huge problems for the town of Polokwane, especially considering that water demand is expected to increase by 1.9x the 2001 value by 2025 due to the growing population and growing economy. Cullis et al (2011) then explains how these results from the models were used at a workshop for stakeholders in Polokwane, where it was concluded that greater priority needs to be placed on water conservation and demand management. The stakeholders also realised the urgent need to reduce future demand for water by implementing new technologies and institutional structures to more effectively manage and conserve water supply.